WebServices - how to get a current index from a recurring appointment

Hello,

I'm importing calendar appointments from Exchange into an ERP system. What I'm trying to figure out are recurring appointments. If I fetch an Appointment from the calendar view and it's a recurring appointment of the AppointmentType=Occurrence... how can I get the OccurenceIdx from that one?

Example:

                foreach (Appointment localAppointment in searchResults)
                {
                    localAppointment.Load(appointmentProperties);
                    if (localAppointment.AppointmentType == AppointmentType.Exception || localAppointment.AppointmentType)

                    {

                                        //TODO: print CurrentIndex

                }

 My understanding is, that all appointments in a series have the same UniqueId... is that correct?

Many thanks,

Martin